Levels

    Like the original Half-Life, the game is divided into chapters:
  1. Point Insertion - Gordon arrives in City 17 and meets up with old friend Barney Calhoun, the security guard from Black Mesa. (Barney is working undercover for the resistance)
  2. A Red Letter Day - Gordon meets Alyx Vance (the daughter of Dr. Eli Vance, who Gordon knows from Black Mesa). Alyx takes him to Dr. Isaac Kleiner (Gordon's mentor from MIT and colleague at Black Mesa). Kleiner attempts to teleport Gordon to Eli's laboratory on the far side of the city but Doctor Kleiner's headcrab "Hedy Lamarr" jumps into the teleporter. This messes up the teleporter and now Gordon must make his way there the hard way.
  3. Route Kanal - Gordon makes his way along the city's canals to find a resistance base. Along the way he runs into aliens he met in Half-life. The resistance provides him with an air boat to get him the rest of the way to Eli's lab.
  4. Water Hazard - Gordon is chased along the city's waterways by Combine troops and a Combine hunter-killer assault helicopter. In the end of episode, luckily, Gordon manages to take it down with the gun on his air boat. (this is technically a boss fight)
  5. Black Mesa East - Gordon arrives at Eli's lab and gets acquainted with Dr. Judith Mossman. Alyx shows him how to use a Gravity Gun. Suddenly the lab is infiltrated by Combine forces and Gordon escapes along the old tunnel to the ominously dark Ravenholm.
  6. "We Don't Go To Ravenholm..." - Gordon meets Father Grigori, who helps him get through the zombie-infested ghost town of Ravenholm to the abandoned mines. The mines lead Freeman to the dockyards outside City 17.
  7. Highway 17 - Gordon finds another resistance base under assault by Combine troops. Alyx tells him that Eli has been captured by the Combine and is being held in Nova Prospekt, an old maximum-security prison. Gordon heads up the coast road in a dune buggy in an attempt to find Eli. The task is somewhat hardened by the fact that it's a spawning season for antlions, so the coast is crawling with them.
  8. Sandtraps - Gordon arrives at the resistance base at Lighthouse Point and must continue the rest of the way to Nova Prospekt on foot. The antlions lie burrowed everywhere, catching the slightest vibrations; so a single step on the sand sets them alarmed and angry, therefore Gordon must cling to the rocks. After Gordon successfully manages to defeat the Antlion Guard he receives the bugbait, a globe filled with pheromones that allows Gordon to control Antlions to his benefit.
  9. Nova Prospekt - Gordon makes his way through the prison's old corridors and basements to try to find where the Combine is holding Eli. This undertaking might have been impossible, had he been not given a means to command the fierce antlions at his will - a pheropod, or a "bug-bait".
  10. Entanglement - Alyx shows up and together they find Eli... and Judith Mossman, who, apparently, is working for the Combine. Eli is teleported out of the prison by the traitor, and Alyx and Gordon escape via Combine teleport to Dr. Kleiner's lab.
  11. Anticitizen One - News of Gordon's successes have sparked an uprising against the Combine and City 17 is in turmoil. Alyx and Gordon survive the teleport, but a malfunction in the system causes their arrival to be delayed by a week. Gordon leads a squad of resistance fighters to free Eli from the monstrous Citadel, while Alyx helps Dr. Kleiner escape the lab.
  12. "Follow Freeman!" - Gordon helps Barney Calhoun, who is pinned down by snipers. Together they shut down the suppressor field. Then Gordon leads the resistance forward and eliminates a pack of Combine war-machines - the Striders.
  13. Our Benefactors - Gordon gets inside the Citadel through an underground passage. To get to its heart he has to climb inside a prisoner pod. The pod brings him to a confiscation room, where the Combine destroys all of his weapons using a special confiscation field. All but one - the Gravity Gun, based on a mysterious Xen technology, somehow causes a "confiscation field failure", and instead of being destroyed gets immensely stronger, infused with Dark Energy. Henceforth it can manipulate organic matter (killing it instantly), large-scale objects and "energy balls". Gordon has to dispatch all of the opposition, using only the Gravity Gun. In the end, however, he is again forced to climb in the prisoner pod, as there is no other way further.
  14. Dark Energy - The pod brings him directly to Dr. Breen's office. There he meets not only Dr. Breen himself, but also the traitor Judith Mossman. The Gravity Gun is taken from him, this time manually. As it turns out soon, Eli and Alyx (unfortunately captured) are also here. Dr. Breen threatens to send them to the Combine's world, which is hostile environment for humans; and he is going to carry out his threat, when Judith Mossman reveals her true colors--her apparent betrayal only a ploy--and hijacks the console controlling the pods, freeing the prisoners. Dr. Breen, however, manages to escape. He flees to the teleport. Gordon follows him, having recovered his Gravity Gun. The game ends as Freeman succeeds at destroying the portal.